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New Single-Cell Test May Prove Useful in Screening of Drugs

New Single-Cell Test May Prove Useful in Screening of Drugs

April 01, 1995

STANFORD, Calif--A new single-cell biological sensor system may
someday allow rapid screening of cancer agents for biofunctional
activity (see illustration on page 1). The test could be used,
for example, to identify compounds that bind to or block receptors
for biomolecules such as growth factors or other cytokines, or
to highlight potentially harmful metabolites.

Richard N. Zare, PhD, who headed the research in the Department
of Chemistry at Stanford University, told Oncology News International
that the technique may have an "important impact in cancer
research, depending on how well we develop a library of receptors
that we can place on cells."

Cells with known receptors could be used as biosensors to screen
compounds for the presence of the ligand that binds to that receptor,
he said.

The technique uses the responses of single cells to detect individual
biomolecules separated from complex chemical mixtures by capillary
electrophoresis. This method solves a past problem with biological
sensors in that a cell can respond to many different biological
compounds. "So when a cell reacts to something in a mixture,
it is difficult to identify just what the cell is responding to.
Capillary electrophoresis allows us to identify the specific compounds
that are triggering the reaction," Dr. Zare said.

How It Works

The separation of a compound takes place in a fused silica capillary
with an inside diameter of 25 microns, a fraction of the size
of a human hair. Each type of molecule moves through the liquid
in the capillary at a different rate, depending on its electrical
charge, size, shape, and other factors.

When a separated biomolecule reaches the end of the capillary
(a process that takes between 5 and 30 minutes), it is directed
onto the single-cell biosensor, positioned on a microscope. In
this way, a tiny amount of a given chemical can be delivered to
an individual cell.